U.S. President Barack Obama greets Yoland Renee King at the 50th anniversary of the March on WashingtonU.S. President Barack Obama greets Yolanda Renee King, granddaughter of Martin Luther King Jr., during a ceremony at the Lincoln Memorial August 28, 2013 to commemorate the 50th anniversary of the March on Washington and Reverend Martin Luther King Jr.'s "I have a dream" speech. REUTERS/Kevin Lamarque

Obama and Oprah Winfrey during the 50th anniversary of the March on WashingtonU.S. President Obama clasps hands with Oprah Winfrey during the commemoration of the 50th anniversary of the March on Washington and Reverend Martin Luther King Jr.'s "I have a dream" speech at the Lincoln Memorial in Washington August 28, 2013.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS CIVIL UNREST ANNIVERSARY ENTERTAINMENT)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People take shelter from the rain during the 'Let Freedom Ring Commemoration and Call to Action' honoring the 50th anniversary of the historic March on Washington for Jobs and Freedom on the National Mall August 28, 2013 in Washington, DC. The 1963 landmark civil rights event was where Dr. Martin Luther King Jr. delivered his famous speech, saying, 'I still have a dream, a dream deeply rooted in the American dream...one day this nation will rise up and live up to its creed, 'We hold these truths to be self evident: that all men are created equal.' I have a dream . . .'

US President Obama walks past church bell before speaking at the Lincoln Memorial in WashingtonU.S. President Barack Obama walks to the podium to speak at the Lincoln Memorial during ceremonies celebrating the 50th anniversary of the 1963 "March on Washington" in Washington August 28, 2013. An address Obama and nationwide bell-ringing will cap celebrations today marking the 50th anniversary of civil rights leader Reverend Martin Luther King Jr.'s landmark "I Have a Dream" speech. The bell is from a church in Birmingham, Alabama. REUTERS/Gary Cameron (UNITED STATES - Tags: ANNIVERSARY POLITICS SOCIETY)

Young, former US president Carter, Johnson, former US President Clinton, Winfrey, US first lady Obama, Kennedy, and US President Obama attend ceremonies celebrating the anniversary of the "March on Washington" in WashingtonAndrew Young (L-R), former U.S. president Jimmy Carter, Lynda Bird Johnson, former U.S. President Bill Clinton, Oprah Winfrey, U.S. first lady Michelle Obama, Caroline Kennedy, and U.S. President Barack Obama attend ceremonies celebrating the 50th anniversary of the 1963 "March on Washington" at the Lincoln Memorial in Washington August 28, 2013. REUTERS/Gary Cameron

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People gather around the reflecting pool while attending the ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

U.S. President Barack Obama speaks at the 50th anniversary of the March on WashingtonU.S. President Barack Obama speaks from the steps of the Lincoln Memorial during the commemoration of the 50th anniversary of the March on Washington and Reverend Martin Luther King Jr.'s "I have a dream" speech in Washington August 28, 2013. The bell behind Obama had hung in the 16th Street Baptist Church in Birmingham, Alabama, before the church was bombed in 1963 just weeks after King's famous speech.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS CIVIL UNREST ANNIVERSARY)

Maori group perform during March on Washington ceremony in WashingtonMembers of a Maori group from New Zealand perform during a ceremony marking the 50th anniversary of Martin Luther King Jr.'s "I have a dream" speech on the steps of the Lincoln Memorial in Washington, August 28, 2013. REUTERS/Jason Reed

U.S. President Barack Obama speaks at the 50th anniversary of the March on WashingtonA TV screen at the bottom of the steps plays as U.S. President Barack Obama speaks from the top of the steps of the Lincoln Memorial during the commemoration of the 50th anniversary of the March on Washington and Martin Luther King Jr.'s "I have a dream" speech in Washington August 28, 2013. REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS ANNIVERSARY)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People gather around the refelcting pool while attending the ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Obamas and Clinton attend the 50th anniversary of the March on Washington in WashingtonFormer U.S. President Bill Clinton, first lady Michelle Obama and U.S. President Obama attend the commemoration of the 50th anniversary of the March on Washington and Martin Luther King Jr.'s "I have a dream" speech at the Lincoln Memorial in Washington August 28, 2013.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS ANNIVERSARY)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: U.S. President Barack Obama

Obama and Oprah Winfrey during the 50th anniversary of the March on WashingtonReflected in a puddle, U.S. President Obama and Oprah Winfrey (R) listen to a speaker during the commemoration of the 50th anniversary of the March on Washington and Reverend Martin Luther King Jr.'s "I have a dream" speech at the Lincoln Memorial in Washington August 28, 2013.
REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS CIVIL UNREST ANNIVERSARY ENTERTAINMENT)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People sit in the rain during a ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom , August 28, 2013 in Washington. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

U.S. President Barack Obama speaks at the Lincoln Memorial on the 50th Anniversary of the March on WashingtonU.S. President Barack Obama speaks at the Lincoln Memorial on the 50th Anniversary of the March on Washington August 28, 2013. REUTERS/James Lawler Duggan (UNITED STATES - Tags: POLITICS ANNIVERSARY CIVIL UNREST)

Obamas, Carter and Clinton wave during the 50th anniversary of the March on Washington(L-R) U.S. President Barack Obama, former President Jimmy Carter, first lady Michelle Obama and former President Bill Clinton wave from the steps of the Lincoln Memorial during the commemoration ceremony for the 50th anniversary of the March on Washington and Reverend Martin Luther King Jr.'s "I have a dream" speech in Washington August 28, 2013. REUTERS/Kevin Lamarque

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People march from Capitol Hill to the Lincoln Memorial during the 'Let Freedom Ring Commemoration and Call to Action' honoring the 50th anniversary of the historic March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. The 1963 landmark civil rights event was where Dr. Martin Luther King Jr. delivered his famous speech, saying, 'I still have a dream, a dream deeply rooted in the American dream...one day this nation will rise up and live up to its creed, 'We hold these truths to be self evident: that all men are created equal.' I have a dream . . .'

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: A member of a Junkanoo band performs during the 'Let Freedom Ring' ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom , August 28, 2013 in Washington. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Obama speaks during a ceremony marking the 50th anniversary of Martin Luther King's "I have a dream" speech in WashingtonU.S. President Barack Obama speaks during a ceremony marking the 50th anniversary of Martin Luther King Jr.'s "I have a dream" speech on the steps of the Lincoln Memorial in Washington, August 28, 2013. REUTERS/Jason Reed

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People take shelter from the rain during the 'Let Freedom Ring Commemoration and Call to Action' honoring the 50th anniversary of the historic March on Washington for Jobs and Freedom on the National Mall August 28, 2013 in Washington, DC. The 1963 landmark civil rights event was where Dr. Martin Luther King Jr. delivered his famous speech, saying, 'I still have a dream, a dream deeply rooted in the American dream...one day this nation will rise up and live up to its creed, 'We hold these truths to be self evident: that all men are created equal.' I have a dream . . .'

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: A dancer performs during the 'Let Freedom Ring' ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom , August 28, 2013 in Washington. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: Signs reading 'We Demand Equality For All' lie on the ground after being given out during the ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People take shelter from the rain during the 'Let Freedom Ring Commemoration and Call to Action' honoring the 50th anniversary of the historic March on Washington for Jobs and Freedom on the National Mall August 28, 2013 in Washington, DC. The 1963 landmark civil rights event was where Dr. Martin Luther King Jr. delivered his famous speech, saying, 'I still have a dream, a dream deeply rooted in the American dream...one day this nation will rise up and live up to its creed, 'We hold these truths to be self evident: that all men are created equal.' I have a dream . . .'

Barack Obama speaks with Yolanda Renee King during March on Washington ceremony in WashingtonU.S. President Barack Obama (bottom L) speaks with Yolanda Renee King, daughter of Martin Luther King III (R ) and his wife Arndrea Waters King (C) at the end of a ceremony marking the 50th anniversary of Martin Luther King Jr.'s "I have a dream" speech on the steps of the Lincoln Memorial in Washington, August 28, 2013. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS ANNIVERSARY)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People take shelter from the rain during the 'Let Freedom Ring Commemoration and Call to Action' honoring the 50th anniversary of the historic March on Washington for Jobs and Freedom on the National Mall August 28, 2013 in Washington, DC. The 1963 landmark civil rights event was where Dr. Martin Luther King Jr. delivered his famous speech, saying, 'I still have a dream, a dream deeply rooted in the American dream...one day this nation will rise up and live up to its creed, 'We hold these truths to be self evident: that all men are created equal.' I have a dream . . .'

US President Obama applauds the ringing of a church bell while the daughter of Martin Luther King III holds her ears during ceremonies celebrating the anniversary of the "March on Washington" in WashingtonU.S. President Barack Obama (L) applauds the ringing of a Birmingham, Alabama church bell while Yolanda Renee King, the daughter of Martin Luther King III (not pictured), holds her ears next to her mother Andrea Waters (R) during ceremonies celebrating the 50th anniversary of the 1963 "March on Washington" at the Lincoln Memorial in Washington August 28, 2013. REUTERS/Gary Cameron

Michelle Obama hugs Arndrea Waters King during March on Washington ceremony in WashingtonU.S. first lady Michelle Obama (L) hugs Arndrea Waters King, wife of Martin Luther King III (R), at the end of a ceremony marking the 50th anniversary of Martin Luther King Jr.'s "I have a dream" speech on the steps of the Lincoln Memorial in Washington, August 28, 2013. Also pictured is their daughter Yolanda. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS ANNIVERSARY)

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: Former U.S. President Bill Clinton speaks during the ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On WashingtonWASHINGTON, DC - AUGUST 28: People sing along to gospel music during a ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.

Junkanoo performs during a ceremony marking the 50th anniversary of Martin Luther King's "I have a dream" speech in WashingtonMembers of Junkanoo perform during a ceremony marking the 50th anniversary of Martin Luther King's "I have a dream" speech on the steps of the Lincoln Memorial in Washington, August 28, 2013. REUTERS/Jason Reed

Obama, Former Presidents Commemorate 50th Anniversary Of MLK's March On Washington

WASHINGTON, DC - AUGUST 28: People gather around the reflecting pool while attending the ceremony to commemorate the 50th anniversary of the March on Washington for Jobs and Freedom August 28, 2013 in Washington, DC. It was 50 years ago today that Martin Luther King, Jr. delivered his 'I Have A Dream Speech' on the steps of the Lincoln Memorial.